The present invention relates to an ocular lens material, and more particularly to an ocular lens material which is high in oxygen permeability and excellent in rigidity and hydrophilic property, and which is suitable for use as contact lenses, intraocular lenses, and the like.
In the field of contact lenses, studies concerning a high oxygen-permeable material have been progressed in recent years. For instance, there have developed contact lenses made of a copolymer comprising, as main components, a siloxanylalkyl methacrylate and methyl methacrylate, contact lenses made of a copolymer comprising, as main components, a siloxanylalkyl methacrylate and a fluoroalkyl methacrylate, and the like.
However, the contact lenses made of these copolymers should be necessarily decreased in the amount of the siloxanylalkyl methacrylate from the viewpoint of hardness and rigidity. Accordingly, it is difficult to obtain contact lenses having high oxygen permeability and excellent mechanical strength.
Also, the contact lenses made of the above-mentioned copolymers are high in water repellency. Accordingly, when a hydrophilic monomer such as methacrylic acid, 2-hydroxyethyl methacrylate or N-vinylpyrrolidone is used in a large amount for giving hydrophilic property, the water absorbancy of an obtained contact lens material improves, but the shape stability of contact lenses made thereof is impaired.
In order to solve the above-mentioned defects, as a hard contact lens material, for instance, an alternating copolymer comprising N-vinyl lactam and fumarate or maleate has been proposed (Japanese Unexamined Patent Publication No. 99913/1991 ). The hard contact lens material is a copolymer containing about 50% by mole of N-vinyl lactam, and is low in water absorption and relatively excellent in hydrophilic property. However, for improving the oxygen permeability, a large amount of a silicon-containing fumarate or a silicon-containing maleate must be used as the fumarate or maleate component, thus resulting in lowering of the hardness and hydrophilic property of the material.
An object of the present invention is to provide an ocular lens material which is simultaneously excellent in all of oxygen permeability, mechanical strength and hardness, and moreover excellent in hydrophilic property in spite of its low water absorption.
This and other objects of the present invention will become apparent from the following description.